Rehabilitation Engineering Research Center for Wireless Technologies Georgia Institute of Technology

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Findings – CMAS

In examining the provisions of CMAS, the team determined that though the field trial methodology used would remain the same, the pre and post test questionnaires needed to be modified to gather data that specifically addressed CMAS specifications, as well as the refinements added to the WEC method. New questionnaires covered personal use (or lack thereof) of TTS software, types of alerts participants are interested in receiving (i.e., weather, terror, health threats), voice quality of the TTS software, the adequacy of message length, content, vibration and/or audio attention signal strength, length and volume, and how to enhance message content (i.e., use of graphics, video, etc.). In order to compare the WEC and CMAS methods we repeated questions that were posed in the WEC method field trials regarding how they currently receive emergency alerts, whether CMAS method was an improvement over current methods, and how to improve the system tested.

100% of CMAS field trial participants had a personal or business mobile device prior to the test. We asked users if they had TTS software on their mobile devices. 41% of the visually impaired users in this test did not have TTS software on their mobile devices. Had this been an actual emergency and not a test, they would not have heard the content of the alert, as the CMAS rules do not require embedded or encoded TTS within the alert message. In order to ensure that all cell phone users, regardless of sensory limitation receive the alert and are capable of accessing the content within the message, TTS would need to be (1) part of the message, or (2) CMAS capable handsets would need to be required to have TTS pre-loaded. To provide “functional equivalency” to a national alerting system, the rules would need to eliminate the added expense that a visually impaired user would incur to receive CMAS alerts by providing solution one or two noted above.

Figure 10: Chart – Does your mobile phone have text-to-speech software?

Following are graphs depicting a side-by-side comparison of vision impaired participants with hearing impaired participants to gain an understanding of the different needs and preferences based on sensory limitation.

Figure 11: Graph - Did the alert message provide good information?

The quality or value of the information in the alert message received a good statistical rating among both the visually impaired (86%) and hearing impaired (82%). The percentage that did not think the information was good commented that “it explained what was happening, but too general as to where the disaster was occurring”; “would have wanted more specific instructions on what to do”; and “insufficient information.” Though the aggregate percentage of participants that found the information of little value is small compared to those that did (15% and 85% respectively); if you apply that 15% to a large population it becomes statistically significant. For example, in the Atlanta Urbanized Metro Area 378,132 non-institutionalized persons age 21 to 64 years have a disability.1 Applying our data to the Atlanta population of people with disabilities translates into 56,719 people who may find the emergency information insufficient. Insufficient emergency information reduces the likelihood of the individual taking the appropriate protective actions in a timely manner. Of course, this is an illustrative example, but it exemplifies the potential impact an uninformed public could have not only on their personal protection, but on the volume of calls for emergency assistance; taxing an already stressed emergency response effort during widespread disasters such as the Atlanta Tornadoes of 2008.

Figure 12: Graph Showing Satisfaction with Length of Message

In the main, the majority of all participants (70%) responded that the CMAS message length was “just right”, with the visually impaired group finding the 90 character message length more satisfactory than the hearing impaired group. Among the hearing impaired respondents 46% found the message was “too short” and 56% thought it was “just right.” Among the visually impaired respondents, 29% found it was “too short” while 71% found it was “just right.” 0% of respondents selected that the test message was “too long.” This begs the question, how much more information could be provided in the message before it became too much? What is the optimal amount of information for an emergency alert to a mobile device?2 Would more detailed information in the initial message facilitate speedier and more appropriate protective measures taken by the recipient?

A 2004 report for Congress on EAS and All Hazard Warnings identified deficiencies in the system, one of which was “limited ability to…provide directions for action to be taken by the general public” due, in part “to the capacity of technology to relay detailed messages.”3 Currently, the CMAS shares this shortcoming, suggesting a need to harmonize the human need for detailed information via a single device with the capacity of the network in which the device operates. Such a consideration brings in topics such as wireless spectrum, public safety networks and priority access, underscoring the inter-reliant nature of emergency alerts and the advanced communications ecosystem. Human factors and preferences suggest technical improvements; and in the best of cases drive development. In the CMAS case, with regard to message length/content, CMAS field trial findings indicate that the human factor is discordant to industry preference and technical requisite to limit character length, suggesting a need for technological inquiry and policy interventions.

Figure 13: Graph - Was the vibration attention signal strong enough to get your attention?

The hearing impaired group found the vibration strength least satisfactory.4 Visually impaired users, with no hearing loss, could rely on the sound attention signal and the vibrating cadence to notify them of incoming alerts; users with significant hearing loss relied solely on the vibrating cadence. In open discussion and on the comments section of the questionnaires, many of the hearing impaired users recommended a light or screen flash function be added to the attention signal. People without sensory limitation can utilize multiple sensory cues to alert them to incoming calls or text messages whether carrying it on their body, in a bag, or even if it is sitting across the room. They may hear it, feel the vibration or hear the vibration on a tabletop. If one of their senses does not pick up the signal another usually will. For those with significant hearing loss the other sense employed for recognition of incoming alerts would be sight. However, the CMAS rules do not require the use of light as an indicator that an alert is incoming. Future rulemakings on CMAS, in its second generation, should seek comments on the need to require visual cues, as well as vibration and sound. This would further ensure accessibility for most people with sensory limitations; no less than two of their senses would be engaged to notify them of incoming alerts, greatly increasing the likelihood of the timely receipt of such alerts.

Figure 14: Graph - Was the sound alert attention signal loud enough and/or long enough to get your attention?

The sound alert attention signal for all users received a 70% satisfactory rate. Among the visually impaired users 86% stated it was loud enough to notify them of incoming alerts; and 50% of hearing impaired users (those who were not profoundly deaf) stated it was loud enough. This finding reiterates the need for more than one sense to be engaged in attention signals.

The following graphs compare the aggregate, hearing impaired and visually impaired participants’ answers to the question: Was this an improvement over how you currently receive emergency alerts?

Figure 15: Graphs - Was this an improvement over how you currently receive emergency alerts?

The visually impaired participants were significantly more pleased with the CMAS alerting compared with their current method of receiving emergency alerts. Some, specific comments were:

  • Because I don't have this type of alert. If you were away from other devices (TV, computer) you would still receive alert.

  • Because I really don't unless people call to tell me what's going on.

  • Because it was mobile and portable. It will be with me wherever I go.

  • Because it talks and tells what type of alert it is.

The aggregate of those that did not find it an improvement (15%) stated it was “about the same [as current method];” “I currently receive emergency text messages from the weather service;” and “Yes and no. Need the vibration to be felt immediately if it is in my pocket.”


Below are specific comments in response to the question “Do you have any suggestions for improving the system you tried today?”

  • More information about where to go or what to do. Improve voice quality.

  • Make voice louder. In a crowded setting it might not be heard. More information should be provided.

  • Make sure first word would come through clearly. Repeated four times and still wasn't clear.

  • Signal should be louder and more distinct and repeated.

  • Repeat the message at least twice. Text point size could be larger.

  • More specific info. Or maybe where to go to find further information.

  • The alert system needs to keep going off until it’s manually turned off.

  • More detailed information, specific locations or sector. Atlanta is too large for this alert to be effective.

  • There needs to be a delay between the alert tone and the voice.

  • Color code message in red or blue (flashing) in addition to voice or display. 'ALERT' flashing during message delivery. Additionally use large fonts.

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